GLOBAL CLIMATE CHANGES AND MOISTURE CONDITIONS IN THE INTRACONTINENTAL ARID ZONES

In order to estimate a transient response of the local hydrological cy cle and vegetation cover in the African monsoon area to global climate changes, a simple two-dimensional water vapor transport model coupled with a carbon cycle model for the soil was used. The key difference f rom other models is that we take into account a positive feedback betw een the precipitation and development of the vegetation root system in the underlying surface. As our calculation shows, this feedback is re sponsible for a long-term transient response of local hydrological cyc les to the global temperature changes. In the case of a four component vegetation system - tropical forests, savannah, semi desert and deser t, (and 2-degrees-C ocean surface water warming), a new steady-state i s reached in about 1500 years. In previous works of other authors, the increase of summer precipitations during Holocene or Last Interglacia l could be explained only as a result of the surface temperature incre ase in the intracontinental parts of Africa. However, from paleodata i ndicates, the temperature in the intracontinental regions of Africa ra ther decreased during warm epochs of geological past: Holocene optimum , Last Interglacial and middle Pliocene climatic optimum. Our simple m odel simulations agree with both paleoprecipitation and paleotemperatu re data.